1. Field of the Invention
This invention relates to a method of determining the quality of ready-mixed concrete for use in checking, confirming or guaranteeing the quality of the ready-mixed concrete. More particularly, the invention relates to a method and apparatus for measuring the quantity of an admixture in ready-mixed concrete in order to determine the quality of the ready-mixed concrete.
2. Description of the Related Art
Conventionally, the guarantee of quality of ready-mixed concrete of this type is based on slump, the quantity of air mixed into the ready-mixed concrete and the strength of the ready-mixed concrete. These aspects have a great influence on variations in strength following molding and solidification of the concrete and on the durability of the resulting structures. The Japanese Industrial Standard (JIS A5308) requires all three characteristics of ready-mixed concrete to be confirmed in the course of manufacture or shipment of the ready-mixed concrete. Slump is a measure of softness of ready-mixed concrete which is greatly influenced by the quantity of water mixed into the ready-mixed concrete (an air entraining agent, an AE water reducing agent, a high-performance AE water reducing agent and other chemical admixtures for concrete kneaded together at a fixed temperature and mixed with water).
On the other hand, the quantity of an admixture or admixtures mixed into ready-mixed concrete is an important factor greatly influencing the quantity of air and strength.
When ordering ready-mixed concrete, the user of the ready-mixed concrete entrusts the manufacturer with use of admixtures which play an important role in determining the concrete quality as noted above. On the site of operation, the ready-mixed concrete is used after a confirmation is made only of slump and quantity of air.
The quantity of admixtures in ready-mixed concrete has not been confirmed heretofore since the admixture content in the ready-mixed concrete cannot be measured with ease. The user must rely on a report from the manufacturer for the quality of concrete in this respect. Thus, quality control has not been made in the normal routine of operation.
Under the circumstances, the quality of ready-mixed concrete is judged on the site of operation only by appearance and intuition based on experience. For example, admixtures are added in a quantity exceeding a predetermined quantity to the ready-mixed concrete containing low quality aggregate for passing a slump test or the like. In a strength test, the ready-mixed concrete to be used is sampled at the start of use, and compressive strength is measured after molding and curing the test pieces. Therefore, results of the strength measurement are available only upon the lapse of 28 days after the curing.